About an hour later, a new message said that a ventilator was being used so that the boy's organs could be donated, adding that family and friends can visit him at Miami Children's Hospital during visiting hours Sunday.

"Even though Zac has passed, he will still be saving many lives," this new post said.

Zachary's family told CNN affiliate WBBH they believe that the boy -- who they described as an active seventh-grader -- was infected while kneeboarding with friends in a water-filled ditch by his house on August 3.

After he was hospitalized, the boy underwent brain surgery, and doctors diagnosed him with primary amoebic meningoencephalitis, according to WBBH.

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Officials warn of brain-eating amoeba

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Officials warn of brain-eating amoeba01:36

After news emerged regarding Zachary's diagnosis, the Florida Department of Health issued a warning to swimmers that high water temperatures and low water levels provide the perfect breeding ground for this rare amoeba.

Between 2001 and 2010, there were only 32 reported cases of people getting Naegleria fowleri in the United States, according to the CDC. Most of the cases have been in the Southeast.

Naegleria fowleri is found in hot springs and warm freshwater, most often in the Southeastern United States. The amoeba enters the body through the nose and travels to the brain. There is no danger of infection from drinking contaminated water, the CDC said.

"This infection is one of the most severe infections that we know of," Dr. Dirk Haselow of the Arkansas Department of Health told CNN affiliate WMC about Kali's case. "Ninety-nine percent of people who get it die."

The first symptoms of primary amoebic meningoencephalitis appear one to seven days after infection, including headache, fever, nausea, vomiting and a stiff neck, according to the Centers for Disease Control and Prevention.

"Later symptoms include confusion, lack of attention to people and surroundings, loss of balance, seizures and hallucinations," the agency website says. "After the start of symptoms, the disease progresses rapidly and usually causes death within one to 12 days."